// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.
//
// Slice is a simple structure containing a pointer into some external
// storage and a size.  The user of a Slice must ensure that the slice
// is not used after the corresponding external storage has been
// deallocated.
//
// Multiple threads can invoke const methods on a Slice without
// external synchronization, but if any of the threads may call a
// non-const method, all threads accessing the same Slice must use
// external synchronization.

#ifndef __RTC_BASE_SLICE_H_
#define __RTC_BASE_SLICE_H_

#include <assert.h>
#include <stddef.h>
#include <string.h>
#include <string>

namespace rtc {

class Slice {
public:
	// Create an empty slice.
	Slice() : buffer_(""), data_(""), size_(0) { }

	// Create a slice that refers to d[0,n-1].
	Slice(const char *d, size_t n) : buffer_(d), data_(d), size_(n) { }

	// Create a slice that refers to the contents of "s"
	Slice(const std::string &s) : buffer_(s.data()), data_(s.data()), size_(s.size()) { }

	// Create a slice that refers to s[0,strlen(s)-1]
	Slice(const char *s) : buffer_(s), data_(s), size_(strlen(s)) { }

	// Return a pointer to the beginning of original buffer
	const char *buffer() {
        return buffer_;
	}

	// Return a pointer to the beginning of the referenced data
	const char *data() const {
		return data_;
	}

	// Return the length (in bytes) of the referenced data
	size_t size() const {
		return size_;
	}

	// Return true iff the length of the referenced data is zero
	bool empty() const {
		return size_ == 0;
	}

	// Return the ith byte in the referenced data.
	// REQUIRES: n < size()
	char operator[](size_t n) const {
		assert(n < size());
		return data_[n];
	}

	// Change this slice to refer to an empty array
	void clear() {
        buffer_ = "";
		data_ = "";
		size_ = 0;
	}

	// Drop the first "n" bytes from this slice.
	void remove_prefix(size_t n) {
		assert(n <= size());
		data_ += n;
		size_ -= n;
	}

	// Return a string that contains the copy of the referenced data.
	std::string to_string() const {
		return std::string(data_, size_);
	}

	// Three-way comparison.  Returns value:
	//   <  0 iff "*this" <  "b",
	//   == 0 iff "*this" == "b",
	//   >  0 iff "*this" >  "b"
	int compare(const Slice &b) const;

	// Return true iff "x" is a prefix of "*this"
	bool starts_with(const Slice &x) const {
		return ((size_ >= x.size_) &&
		        (memcmp(data_, x.data_, x.size_) == 0));
	}

private:
    const char *buffer_;
	const char *data_;
	size_t size_;

	// Intentionally copyable
};

inline bool operator==(const Slice &x, const Slice &y) {
	return ((x.size() == y.size()) &&
	        (memcmp(x.data(), y.data(), x.size()) == 0));
}

inline bool operator!=(const Slice &x, const Slice &y) {
	return !(x == y);
}

inline int Slice::compare(const Slice &b) const {
	const int min_len = (size_ < b.size_) ? size_ : b.size_;
	int r = memcmp(data_, b.data_, min_len);
	if (r == 0) {
		if (size_ < b.size_) {
			r = -1;
		} else if (size_ > b.size_) {
			r = +1;
		}
	}
	return r;
}

}  // namespace rtc

#endif  // __RTC_BASE_SLICE_H_


